1. Field of the Invention
The invention relates to antifoam particles comprising porous copolymers of urea or melamine or of mixtures thereof with an alkanal, and a liquid silicone antifoam composition.
2. Background Art
Pulverulant silicone antifoam agents are known. They may be composed of different carrier materials, suitable for the different applications, and are used, for example, for foam control in powder detergents, as an ingredient in agrochemicals, and in redispersible polymer powders for treating construction materials.
DE 69421462 T2 describes particulate foam control agents in which the silicone antifoam agent has been applied to a zeolite carrier and surrounded with a polycarboxylate encapsulant. To protect the silicone antifoam agent from the alkaline medium of the zeolite carrier, the carrier material must be given an application of an organopolysiloxane/polyoxyalkylene copolymer before the silicone antifoam agent is applied. A disadvantage of this procedure is a comparatively costly and inconvenient operation.
WO 2005/123892 A1 describes active ingredient particles which are composed of a core material consisting of fragrance, silicone fluid, wax, hydrocarbons, higher fatty acids, oil essences, lipids, silicon dioxide particles, and similar active ingredients. Surrounding this core material is a shell material made from polymers such as polyureas, for example. The disadvantage here is that a costly and inconvenient operation is necessary for encapsulating the particle comprising active ingredient, and in some cases this operation has to be carried out at increased temperature.
WO 2008/063625 A1 describes a particle composition composed of one or more particles with a core material and a shell. The core material may be inter alia silicone fluid, silicon dioxide particles, foam control agents or defoamers; the shell material may be inter alia polyurea. Here, again, the polyurea serves for enveloping the particles, and not as a carrier material for the silicone fluid. The process used for producing the encapsulated materials is costly and inconvenient.